Fix all baseline code-review findings across the six shared libraries

Resolves the 35 findings from the 2026-06-01 baseline (commit 26ba1c7),
test-first for every behavioral change. +51 tests (331 -> 382 passing, 0 failed).

- Telemetry-001 (HIGH): RedactionEnricher now honours property removal, so a
  redactor that drops a key actually scrubs the secret from the event.
- Auth: LDAP validator ValidateOnStart; API-key verify no longer fails on a
  best-effort MarkUsed write or a corrupt scopes column (fail-closed); LDAP cert
  validation hook; KeyPrefix persistence aligned; README algorithm corrected.
- Health: Akka checks return Degraded (not throw) when the cluster isn't up yet;
  GrpcDependencyHealthCheck catch-all; null 'description' rendered; composite
  endpoint builder; XML docs shipped.
- Audit: CompositeAuditWriter no longer re-throws OperationCanceledException;
  TruncatingAuditRedactor over-redact scrubs Target + safe negative max; options
  record; XML docs shipped.
- Configuration: TryAddEnumerable idempotent registration; consistent port
  quoting; strict invariant port parsing; XML docs + README packaged.
- Theme: mobile toggle is now CSS-only (no Bootstrap JS); token/CSS hygiene;
  XML docs on the public parameter surface.

Shared-contract/spec docs updated where the code was the source of truth
(observability service.instance.id, MapZbMetrics, redactor reach). All changes
additive/back-compatible at v0.1.0. code-reviews bookkeeping follows separately.

ZB.MOM.WW.Audit/tests/ZB.MOM.WW.Audit.Tests/TruncatingAuditRedactorTests.cs

@@ -53,4 +53,30 @@ public class TruncatingAuditRedactorTests
         var result = r.Apply(Evt(new string('x', 20)));
         Assert.Equal(3, result.DetailsJson!.Length);
     }
+
+    [Fact]
+    public void Negative_max_is_treated_as_zero_and_does_not_throw()
+    {
+        // A negative cap is nonsensical misconfiguration. Truncate must clamp to 0 rather than
+        // throw, capping the value to the empty string (plus marker handling).
+        var opts = new TruncatingAuditRedactorOptions { MaxDetailsJsonLength = -5, MaxTargetLength = -1, TruncationMarker = "" };
+        var r = new TruncatingAuditRedactor(opts);
+        var result = r.Apply(Evt(new string('x', 20), target: new string('y', 20)));
+        Assert.Equal(string.Empty, result.DetailsJson);
+        Assert.Equal(string.Empty, result.Target);
+    }
+
+    [Fact]
+    public void Over_redact_fallback_scrubs_both_details_and_target_without_throwing()
+    {
+        // Drive the REAL TruncatingAuditRedactor.Apply into its catch branch via a reachable
+        // misconfiguration (a null TruncationMarker faults inside Truncate). The over-redact
+        // fallback must be strictly safer: BOTH DetailsJson AND Target scrubbed to null, no throw.
+        var opts = new TruncatingAuditRedactorOptions { MaxDetailsJsonLength = 5, TruncationMarker = null! };
+        var r = new TruncatingAuditRedactor(opts);
+        var raw = Evt(new string('x', 50), target: "sensitive target");
+        var result = r.Apply(raw);
+        Assert.Null(result.DetailsJson);
+        Assert.Null(result.Target);
+    }
 }